Moiré Superlattice Effects and Band Structure Evolution in Near-30-Degree Twisted Bilayer Graphene

Matthew J. Hamer, Alessio Giampietri, Viktor Kandyba, Francesca Genuzio, Tevfik O. Menteş, Andrea Locatelli, Roman V. Gorbachev, Alexei Barinov, Marcin Mucha-Kruczynski

Research output: Contribution to journalArticlepeer-review

Abstract

In stacks of two-dimensional crystals, mismatch of their lattice constants and misalignment of crystallographic axes lead to formation of moiré patterns. We show that moiré superlattice effects persist in twisted bilayer graphene (tBLG) with large twists and short moiré periods. Using angle-resolved photoemission, we observe dramatic changes in valence band topology across large regions of the Brillouin zone, including the vicinity of the saddle point at M and across 3 eV from the Dirac points. In this energy range, we resolve several moiré minibands and detect signatures of secondary Dirac points in the reconstructed dispersions. For twists θ > 21.8°, the low-energy minigaps are not due to cone anticrossing as is the case at smaller twist angles but rather due to moiré scattering of electrons in one graphene layer on the potential of the other which generates intervalley coupling. Our work demonstrates the robustness of the mechanisms which enable engineering of electronic dispersions of stacks of two-dimensional crystals by tuning the interface twist angles. It also shows that large-angle tBLG hosts electronic minigaps and van Hove singularities of different origin which, given recent progress in extreme doping of graphene, could be explored experimentally.
Original languageEnglish
Pages (from-to)1954-1962
Number of pages9
JournalACS Nano
Volume16
Issue number2
Early online date24 Jan 2022
DOIs
Publication statusPublished - 22 Feb 2022

Keywords

  • minigaps
  • moiré superlattices
  • photoemission
  • stacking-dependent electronic properties
  • twisted bilayer graphene
  • van Hove singularities

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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